This invention relates in general to the field of microelectronic device fabrication, and more particularly to a method and apparatus for thin film deposition using an active shutter in a physical-vapor deposition system.
Shutters perform specialized functions in thin film processing, particularly in physical-vapor deposition (PVD) systems, by regulating a division of space within a processing chamber. Typically a first region of the divisible space includes a substrate support for supporting the substrate and in some applications, regulating the temperature of the substrate to be processed. A second region of the divisible space includes a process energy source such as a physical-vapor deposition (xe2x80x9cPVDxe2x80x9d) target electrode. Shutter activation temporarily divides a thin-film processing chamber into two separate regions of space by insertion of the shutter into the processing chamber between the substrate support and the target. Thus, a shutter blocks the line-of-sight view between the target and the substrate.
Shutters support a number of device processing functions including the plasma cleaning of substrates, the surface preparation of targets such as by target burn-in, or timing operations, such as end-pointing or terminating a deposition process involving plasma sputtering effects between the target and substrate. For example, to clean a substrate the shutter is grounded and bias voltage such as an RF bias is applied to the substrate. Similarly, to clean a target a bias voltage such as DC or RF bias is applied to the target. A shutter can help with the substrate and target cleaning operations by preventing cross-contamination between the target and the substrate during these operations. A shutter also helps to reduce process transients by stabilizing PVD plasma generated through target bias with the shutter closed and then opening the shutter to expose the substrate to the target and the sputtering flux initiated from the target.
Typical shutters have an extendible arm assembly that acts to move the shutter, usually a blocking plate, between an open position in which the substrate support is exposed to the target and a closed position in which the shutter intercedes between the substrate support and the target. For instance, an actuator may extend the shutter plate across the processing chamber, with the shutter moving in a plane parallel to the target and the substrate from one side of the process chamber so as to establish a closed position dividing the chamber space. Retraction of the shutter plate from the chamber into a shutter housing attached to the process chamber establishes an open position.
Use of a shutter improves thin film processing in a single chamber but does not address other difficulties associated with deposition of plural thin film layers of different materials. A single target electrode in a PVD processing chamber allows deposition of only the target""s material on the substrate surface within that chamber. Thus, generally thin film processing requiring the sputter deposition of multiple layers of distinct materials onto a substrate involves processing in multiple chambers or vacuum chambers, comprising multiple process stations. Multi-chamber processing tends to increase processing costs with additional processing equipment such as additional chambers, wafer handling equipment for transferring a substrate from one chamber to the next, and extended processing time due to extra wafer handling steps. Also, the movement of a substrate from one chamber to the next often introduces impurities either due to the residual contaminants in the substrate handling hub or particles. For instance, freshly deposited material or particles may break off the edges of the substrate or the transfer equipment during substrate transfer and handling.
One potential solution to the problems related to the deposition of multiple thin film layers is to provide multiple target electrodes in a single vacuum processing chamber. However, single vacuum processing chambers with multiple target electrodes or multiple PVD stations may result in cross-contamination of targets and substrates by the material of the different targets, thereby affecting process reliability and repeatability.
Contamination within the surface of the chamber is another common problem associated with the use of multiple targets in a single deposition chamber. After a number of deposition runs, the deposition chamber often contains impurities that dislodge as particles to disrupt the deposition process. To address this difficulty, the deposition chamber is or the deposition shield typically serviced to remove impurities from the system. Such servicing or shield replacements would have to occur more often if multiple materials are used in a chamber. Frequent servicing disrupts processing flow due to the need for vacuum breaks, consuming valuable time and resources.
Therefore a need has arisen for a method and apparatus for thin film deposition of plural material layers on a substrate which deposits different materials in a single processing chamber.
A further need exists for a method and apparatus for thin film deposition of plural material layers on a substrate which supports deposition of plural materials in a single processing chamber while reducing the maintenance required to manage contaminants at or below a desired level.
A further needs exists for a method and apparatus for thin film deposition of plural material layers on a substrate which increases throughput and-decreases equipment cost, footprint and processing time.
In accordance with the present invention, a method and apparatus for thin film deposition using an active shutter is provided that substantially eliminates or reduces disadvantages and problems associated with previously developed thin film deposition equipment. A shutter target support couples to a shutter so that a target in the shutter target support moves into and out of the processing chamber in conjunction with the shutter. When the shutter is in a closed position, a target in the shutter target support is positioned facing the substrate for deposition of a material on a substrate. When the shutter is in an open position, the shutter target support is substantially removed from the processing chamber to allow deposition of another material on the substrate from a main target located in the processing chamber.
More specifically, in one embodiment a vacuum processing chamber housing has a main target support located in it that supports a target electrode comprised of a first material for deposition on a substrate. The vacuum processing chamber housing also has a substrate support that is generally opposed to the first target support with a direct line-of-sight view so that material of the first target deposits onto a substrate in the substrate support.
A shutter interfaces with the housing through a slot that allows movement of the shutter between a closed position and an open position. When the shutter is positioned in the closed position, the shutter enters through the slot to create a barrier or blockage between the first or main target support and the substrate support. When the shutter is positioned in the open position, the shutter exits the housing through the slot to allow material deposition from the first target onto the substrate.
A shutter target support is coupled to the shutter assembly such that when the shutter is in the closed position, a shutter target associated with the shutter target support substantially aligns with and faces the substrate support. The shutter target associated with shutter target support is comprised of a second PVD target material for deposition on the substrate. In one embodiment, the shutter target support retrofits a conventional shutter to enable conversion of the conventional shutter to support deposition of a second type of material in a single PVD vacuum processing chamber.
The shutter cooperates with the housing to create different regions of space dependent upon the shutter""s position. With the shutter in the open position, the housing defines a region of process space that allows deposition from a main target in the housing, for instance coupled to the top of the housing, onto a substrate. With the shutter in the closed position, the shutter in cooperation with the housing, defines a region of space that allows deposition from a shutter target, coupled to the shutter, onto a substrate, while blocking the main target.
In operation, the present invention deposits thin film layers of plural types of material onto a substrate. For instance, a first thin film layer of material is deposited from a first target or main target located in the processing chamber when the shutter is in an open position. Once the first material is deposited, the shutter moves to a closed position, bringing the shutter target into substantial alignment with the substrate. A second material is then deposited from the shutter target onto the substrate. Deposition of the first and second materials essentially occur in separate regions of space without any cross-contamination between the two targets to reduce the risk of contamination of the substrate. Each target""s process space is established by positioning of the shutter in either an open or closed position with the position open for deposition from the main target and closed for deposition from the shutter target.
The present invention provides a number of important technical advantages. One important technical advantage is the deposition in a single vacuum processing chamber of plural types of materials as thin film layers on a substrate. The association of a target with an active shutter allows deposition of multiple materials with minimal modification to existing single-target equipment. The shutter target support easily couples to conventional PVD shutters, allowing retrofitting of existing single target PVD systems to enable multiple target operation without substantial expense or design changes.
Another important technical advantage of the present invention is the capability of depositing plural materials in a single PVD processing chamber with reduced risk of contamination of the substrate due to cross-contamination between the targets during processing. For instance, the shutter isolates the shutter target during deposition from target(s) located in the processing chamber by retracting the shutter target from the processing chamber away from the main process chamber and into the shutter housing when the shutter is in the open position. Similarly, the shutter isolates targets located in the processing chamber during deposition from the shutter target by inserting the shutter plate between the substrate and the processing chamber targets. The effective isolation of processing chamber target(s) from shutter target(s) minimizes risk of cross-contamination during processing, and reduces maintenance requirements to manage contaminant levels.
Another important technical advantage of the present invention is that it provides increased efficiency and throughput in deposition processes. For instance, deposition of plural materials in a single chamber increases process throughput by eliminating the time generally needed to transfer a substrate among multiple processing chambers. Processing cost is also reduced due to the decreased cost of ownership (COD) for the PVD processing equipment. The use of a single process chamber also reduces the contaminants for multi-layer film processing and reduces equipment footprint.